1. Field of the Invention
The present invention relates to a thermally-stable magnetoresistance effect device, and to a magnetic head, a magnetic recording apparatus, and a magnetoresistance effect memory device using the thermally-stable magnetoresistance effect device.
2. Description of the Related Art
In recent years, in a magnetoresistance effect device including a layered structure of ferromagnetic layer (free layer)/non-magnetic layer/ferromagnetic layer (pinned layer), studies on GMR (giant magnetoresistance) devices which use a metal film, such as Cu or the like, in the non-magnetic layer, and studies on a tunneling-type magnetoresistance effect device, called a TMR device, which uses an insulative film, such as Al2O3 or the like, in the non-magnetic layer, have become enthusiastic (Journal of Magnetism and Magnetic Materials, 139 (1995), L231). Application of the GMR device and the TMR device to a magnetic head and a memory device has been studied (2000 IEEE ISSCC TA7.2, TA7.3). There is already an application of the GMR device to a magnetic head. The TMR device exhibits a magnetoresistance change rate of about 40% at room temperature and is expected to achieve high output.
However, such a magnetoresistance effect device is a layered film having a thickness of several nanometers. At 250xc2x0 C.-300xc2x0 C. or higher, interfacial diffusion is caused in the magnetoresistance effect device, and characteristics of the magnetoresistance effect device deteriorate. Specifically, in a magnetoresistance effect device including an antiferromagnetic layer in which a pinned layer contains Mn, such as FeMn, IrMn, etc., and ferromagnetic layers which are exchange-coupled via the antiferromagnetic layer, at a temperature of 250xc2x0 C. or higher, Mn is diffused, and as a result, characteristics of the magnetoresistance effect device deteriorate.
In order to eliminate such a problem, there is an attempt to form a pinned layer so as to have a structure, ferromagnetic layers/non-magnetic layer for exchange-coupling/ferromagnetic layers, wherein the two ferromagnetic layers are antiferromagnetically exchange-coupled via the non-magnetic layer for exchange-coupling containing Ru, Ir, Rh, etc. In such a structure, diffusion of Mn is prevented by Ru, Ir, Rh, etc.
However, in this case, the thickness of the non-magnetic layer for exchange-coupling is about 0.6-0.8 nm, and thus, at 300xc2x0 C. or higher, diffusion is caused in an interface of the non-magnetic layer for exchange-coupling, whereby characteristics of such a magnetoresistance effect device deteriorate. That is, the above problem cannot be eliminated.
According to one aspect of the present invention, a magnetoresistance effect device includes: a free layer whose magnetization direction is easily rotated by an external magnetic field; a non-magnetization layer; and a pinned layer whose magnetization direction is not easily rotated by an external magnetic field, the pinned layer being provided on a face of the non-magnetization layer which is opposite to a face on which the free layer is formed, wherein the pinned layer includes: a first non-magnetic film for exchange-coupling; and first and second magnetic films which are antiferromagnetically exchange-coupled to each other via the first non-magnetic film, and the first non-magnetic film includes one of the oxides of Ru, Ir, Rh, and Re.
In one embodiment of the present invention, the magnetoresistance effect device is a tunneling-type magnetoresistance effect device.
In another embodiment of the present invention, the magnetoresistance effect device further includes an antiferromagnetic film which is magnetically exchange-coupled to the pinned layer.
In still another embodiment of the present invention, the free layer includes a second non-magnetic layer for exchange-coupling, and third and fourth magnetic films which are antiferromagnetically exchange-coupled to each other via the second non-magnetic film; the second non-magnetic film for exchange-coupling includes one of the oxides of Ru, Ir, Rh, and Re; and the third magnetic film has an intensity of magnetization M1 and a thickness t1 and the fourth magnetic film has an intensity of magnetization M2 and a thickness t2, and a product (M1xc3x97t1) is substantially different from a product (M2xc3x97t2).
In still another embodiment of the present invention, at least one of the first through fourth magnetic films mainly contains cobalt (Co) and also contains boron (B).
In still another embodiment of the present invention, at least one of the first and second magnetic films mainly contains cobalt (Co) and also contains boron (B).
In still another embodiment of the present invention, the magnetoresistance effect device further includes: an antiferromagnetic layer which is magnetically exchange-coupled to the pinned layer; and an underlying layer mainly containing NiFeCr, the underlying layer being provided on a face of the antiferromagnetic layer which is opposite to a face on which the pinned layer is formed.
According to another aspect of the present invention, a magnetoresistance effect device includes: a free layer whose magnetization direction is easily rotated by an external magnetic field; a non-magnetization layer; and a pinned layer whose magnetization direction is not easily rotated by an external magnetic field, the pinned layer being provided on a face of the non-magnetization layer which is opposite to a face on which the free layer is formed, wherein the free layer includes: a first non-magnetic layer for exchange-coupling; and first and second magnetic films which are antiferromagnetically exchange-coupled to each other via the first non-magnetic film, the first non-magnetic film includes one of the oxides of Ru, Ir, Rh, and Re, and the first magnetic film has an intensity of magnetization M1 and a thickness t1 and the second magnetic film has an intensity of magnetization M2 and a thickness t2, and a product (M1xc3x97t1) is substantially different from a product (M2xc3x97t2).
In one embodiment of the present invention, the magnetoresistance effect device is a tunneling-type magnetoresistance effect device.
In another embodiment of the present invention, the magnetoresistance effect device further includes: an antiferromagnetic layer which is magnetically exchange-coupled to the pinned layer; and an underlying layer mainly containing NiFeCr, the underlying layer being provided on a face of the antiferromagnetic layer which is opposite to a face on which the pinned layer is formed.
According to still another aspect of the present invention, a magnetic head for detecting a signal magnetic field from a recording medium includes: two shield sections each including a magnetic substance; and the magnetoresistance effect device of the present invention provided in a gap between the two shield sections.
According to still another aspect of the present invention, a magnetic head includes: a magnetic flux guiding section including a magnetic substance; and the magnetoresistance effect device of the present invention for detecting a signal magnetic field introduced by the magnetic flux guiding section.
According to still another aspect of the present invention, a magnetic recording medium includes: the magnetic head of the present invention for recording a signal in a recording medium; an arm on which the magnetic head is mounted; a driving section for driving the arm; and a signal processing section for processing the signal and supplying the processed signal to the magnetic head.
According to still another aspect of the present invention, a magnetoresistance effect memory device includes: a magnetoresistance effect device including a free layer whose magnetization direction is easily rotated by an external magnetic field, a non-magnetization layer, and a pinned layer whose magnetization direction is not easily rotated by an external magnetic field, the pinned layer being provided on a face of the non-magnetization layer which is opposite to a face on which the free layer is formed, wherein the pinned layer includes: a non-magnetic film for exchange-coupling; and first and second magnetic films which are antiferromagnetically exchange-coupled to each other via the non-magnetic film, the non-magnetic film for exchange-coupling includes one of the oxides of Ru, Ir, Rh, and Re; a word line for generating a magnetic field so as to invert the magnetization direction of the free layer; and a sense line for detecting a change in resistance of the magnetoresistance effect device.
In one embodiment of the present invention, the magnetoresistance effect device further includes an antiferromagnetic film which is magnetically exchange-coupled to the pinned layer.
In another embodiment of the present invention, the free layer includes: a second non-magnetic layer for exchange-coupling; and third and fourth magnetic films which are antiferromagnetically exchange-coupled to each other via the second non-magnetic film; the second non-magnetic film for exchange-coupling includes one of the oxides of Ru, Ir, Rh, and Re; and the third magnetic film has an intensity of magnetization M1 and a thickness t1 and the fourth magnetic film has an intensity of magnetization M2 and a thickness t2, and a product (M1xc3x97t1) is substantially different from a product (M2xc3x97t2).
In still another embodiment of the present invention, at least one of the first through fourth magnetic films mainly contains cobalt (Co) and also contains boron (B).
In still another embodiment of the present invention, at least one of the first and second magnetic films mainly contains cobalt (Co) and also contains boron (B).
In still another embodiment of the present invention, wherein the magnetoresistance effect device further includes: an antiferromagnetic layer which is magnetically exchange-coupled to the pinned layer; and an underlying layer mainly containing NiFeCr, the underlying layer being provided on a face of the antiferromagnetic layer which is opposite to a face on which the pinned layer is formed.
According to still another aspect of the present invention, a magnetoresistance effect memory device includes: a magnetoresistance effect device including a free layer whose magnetization direction is easily rotated by an external magnetic field, a non-magnetization layer, and a pinned layer whose magnetization direction is not easily rotated by an external magnetic field, the pinned layer being provided on a face of the non-magnetization layer which is opposite to a face on which the free layer is formed, wherein the free layer includes: a first non-magnetic layer for exchange-coupling; and first and second magnetic films which are antiferromagnetically exchange-coupled to each other via the first non-magnetic film, the first non-magnetic film includes one of the oxides of Ru, Ir, Rh, and Re, and the first magnetic film has an intensity of magnetization M1 and a thickness t1 and the second magnetic film has an intensity of magnetization M2 and a thickness t2, and a product (M1xc3x97t1) is substantially different from a product (M2xc3x97t2); a word line for generating a magnetic field so as to invert the magnetization direction of the free layer; and a sense line for detecting a change in resistance of the magnetoresistance effect device.
In one embodiment of the present invention, the magnetoresistance effect device further includes: an antiferromagnetic layer which is magnetically exchange-coupled to the pinned layer; and an underlying layer mainly containing NiFeCr, the underlying layer being provided on a face of the antiferromagnetic layer which is opposite to a face on which the pinned layer is formed.
According to still another aspect of the present invention, a memory device which is formed by the magnetoresistance effect devices of the present invention arranged in a matrix.
In one embodiment of the present invention, each of the magnetoresistance effect devices further includes: an antiferromagnetic layer which is magnetically exchange-coupled to the pinned layer; and an underlying layer mainly containing NiFeCr, the underlying layer being provided on a face of the antiferromagnetic layer which is opposite to a face on which the pinned layer is formed.
According to a magnetoresistance effect device of the present invention, an oxide film of Ru, Ir, Rh, or Re is used in a non-magnetic layer for exchange-coupling. In such a structure, diffusion of Ru, Ir, Rh, or Re at an interface of the non-magnetic layer for exchange-coupling is suppressed, and as a result, a heat-resisting property of the device is significantly improved. A hard-magnetic film may be used as a pinned layer in the magnetoresistance effect device. However, in such a case, when the size of the device is small, a magnetic field of the pinned layer influences a free layer. Thus, it is desirable that the pinned layer be formed of a layered antiferromagnetic coupling film which is magnetically exchange-coupled to an antiferromagnetic film.
In the layered antiferromagnetic coupling film where a first magnetic layer has the intensity of magnetization M1 and thickness t1 and a second magnetic layer has the intensity of magnetization M2 and thickness t2, the first and second magnetic films must be formed such that a product (M1xc3x97t1) is different from a product (M2xc3x97t2) in order to rotate the magnetization direction of the free layer to the direction of externally-applied magnetic field. This is because, in the case where (M1xc3x97t1)=(M2xc3x97t2), even if a magnetic field is applied, the magnetization direction of the free layer is inhibited from rotating to the direction of the applied magnetic field. It is desirable that the pinned layer be formed of the above layered antiferromagnetic coupling film which is magnetically exchange-coupled to an antiferromagnetic film.
A magnetic film which mainly contains cobalt (Co) and contains boron (B) may be used in a portion of a magnetic film(s) of the pinned layer or free layer, or both of the pinned layer and free layer of the magnetoresistance effect device of the present invention. With such a structure, a soft-magnetic characteristic of the free layer is improved, and as a result, a device with improved sensitivity can be obtained.
The above magnetoresistance effect device is provided in a gap between two shields which are made of a magnetic material, whereby a magnetic head which includes a thermally-stable reproduction head for detecting a signal magnetic field can be obtained.
According to the present invention, a magnetic head including a thermally-stable reproduction head which has a magnetic flux guide (yoke) section made of a magnetic material and which uses the above magnetoresistance effect device for detecting a signal magnetic field introduced along the magnetic flux guide section can be obtained.
A magnetic recording apparatus with superior thermal stability can be formed by the above magnetic head, a driving section for the magnetic head, a magnetic recording medium section for recording information, and a signal processing section.
A magnetoresistance effect memory device with superior thermal stability can be formed by the above magnetoresistance effect device, a conductive line (word line) for generating a magnetic field which inverts a magnetic field of the free layer in the magnetoresistance effect device, and a conductive line (sense line) for detecting a change in resistance of the magnetoresistance effect device.
Furthermore, the above memory devices are arranged into a matrix, and a driving circuit is provided thereto, whereby a (random access) memory device with superior thermal stability can be obtained.
Thus, the invention described herein makes possible the advantages of (1) providing a magnetoresistance effect device with improved thermal stability which exhibits stable characteristics even at 400xc2x0 C.; and (2) providing a magnetic head, a magnetic recording apparatus, and a memory device using such a magnetoresistance effect device.
These and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying figures.